A vertical heat treatment apparatus is known in which heat treatment is performed on a plurality of substrates at once by using a wafer boat which is installed in a processing container to be rotated around a predetermined rotary shaft and which holds the plurality of substrates substantially horizontally with a predetermined interval in the vertical direction. In the vertical heat treatment apparatus, when the heat treatment is repeatedly performed, reaction products adhere to the inner wall of the processing container and the wafer boat. The adhered reaction products may float as particles and adhere to the substrates, which may cause a reduction in yield.
In order to avoid this problem, there has been proposed a cleaning technique for removing reaction products adhered to the inner wall of a processing container and a wafer boat by supplying a fluorine-containing gas such as a chlorine trifluoride (ClF3) gas or the like into the processing container.
However, in the proposed technique, when a film forming process is performed after the cleaning, fluorine remaining in the processing container may be adsorbed on the surface of an underlying surface and enter a film, which may deteriorate the device characteristics.